Cross-referencing unnumbered appendix slide in Revealjs presentation

[jpowerj]

Bug description

Hi all,

I'm using Quarto websites, with Quarto+Revealjs slides, for a course I'm teaching in the fall, and absolutely loving everything about it :)

I have a very corner-case issue: I can cross-reference slides perfectly well, except for those I've given the class .unnumbered, which I'm using at the moment for Appendix slides (extra info, answers to questions that may come up, etc.).

As far as I can tell, adding .unnumbered is what's breaking it, as my MWE hopefully shows. But I'm leaving in some of my front matter to show that e.g. slide-number is set to true, as is helpfully mentioned in the docs!

From what I know about pandoc and traversing nodes and etc., it seems like it's probably related to #3234, though in my case it's all within a single .qmd file. And, feel free to close if it's already being fixed in the newer version referenced here

MWE is just the following (and in a gist just in case):

---
title: "Appendix Cross-Ref: MWE"
format:
  revealjs:
    slide-number: true
    number-sections: true
    number-depth: 2
    code-fold: true
    footnotes-hover: true
    scrollable: true
    df-print: kable
---

## First Slide

See @sec-appendix-a. Then see @sec-appendix-b.

## Appendix A: Continuous RV Support {#sec-appendix-a .unnumbered}

First appendix.

## Appendix B: Numbered {#sec-appendix-b}

Second appendix. This one can be referenced

I am using the VSCode extension, so no R Studio version issues I don't think. OS is Windows 11. Here is my quarto check output (I'm omitting the Jupyter part just because, I have a weird Jupyter setup for research stuff, so it just produces a big error that I know how to fix but haven't fixed yet!)

[>] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.1: OK
      Dart Sass version 1.55.0: OK
[>] Checking versions of quarto dependencies......OK
[>] Checking Quarto installation......OK
      Version: 1.3.319
      Path: C:\Users\jpjac\AppData\Local\Programs\Quarto\bin
      CodePage: 1252

[>] Checking basic markdown render....OK

[>] Checking Python 3 installation....OK
      Version: 3.10.5
      Path: C:/Python310/python.exe
      Jupyter: 5.3.0
      Kernels: whatlies, python3

Like I said, I imagine I'm in the same boat as #3234, but would love the ability to cross-reference Appendix slides/sections in future versions! Thanks so much.

Checklist

• Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.
• Please provide the output of quarto check so we know which version of quarto and its dependencies you're running.

[mcanouil]

Note that the class you mentionned is not valid for revealjs, see #5566.

[cderv]

@mcanouil which class are you referring to ? is it .unnumbered ? Sorry but I miss the why about linking to #556. Thanks

@jpowerj I think the cross ref system currently skip on purpose unnumbered headers.

quarto-cli/src/resources/filters/crossref/sections.lua

Lines 12 to 15 in 387e489

	-- skip unnumbered
	if (el.classes:find("unnumbered")) then
	return el
	end

I believe this is mainly because we are creating a reference using the number of the section (replacing @sec-... by Section <number>. If we were to have an option to create a reference using the title itself, it could probably be possible to link to unnumbered section.

This limitation is documented at https://quarto.org/docs/authoring/cross-references.html#sections

Note that when using section cross-references, you will also need to enable the number-sections option

by implicitly meaning that all sections should be numbered

Alternative

As you are in the specific case of revealjs slide here, you can leverage its direct feature though - Revealjs allows you to create internal links (https://revealjs.com/links/)

So you can do

---
title: "Appendix Cross-Ref: MWE"
format:
  revealjs:
    slide-number: true
    number-sections: true
    number-depth: 2
    code-fold: true
    footnotes-hover: true
    scrollable: true
    df-print: kable
---

## First Slide

See [Appendix A](#sec-appendix-a). Then see [Appendix B](#sec-appendix-b)

## Appendix A: Continuous RV Support {#sec-appendix-a .unnumbered}

First appendix.

## Appendix B: Numbered {#sec-appendix-b}

Second appendix. This one can be referenced

This would work in regular single page HTML too as you can create any links to point toward an element with an id.

Hope it helps.

@cscheid assigning to you in case we want to offer a way to cross ref to a unnumber section with our new crossref system.

[mcanouil]

@cderv I meant to reference #5566 (missing 6).

And I was talking about .unnumbered which is about section headers being numbered or not, not slide numbers.

[cderv]

Thanks for clarifying ! wrong issue number makes sense why I did not understood 😅

Regaring numbering, I believe I understand it well and it is about Slide title number and not slide number itself. .unnumbered does the former so I based my answer on this, which I understood from the example.

For slide number, indeed #5566 is what to look for.

[mcanouil]

Yes, it's the following that is a little confusing, since it makes a link between two very different things.

As far as I can tell, adding .unnumbered is what's breaking it, as my MWE hopefully shows. But I'm leaving in some of my front matter to show that e.g. slide-number is set to true, as is helpfully mentioned in the docs!